Summary of proposed work: Work will continue on the biochemical events in the follicles of chickens, rabbits, and pigs between the time the follicles receive hormonal stimuli to the time of ovulation. We plan to determine rates of steroid synthesis and release from preovulatory follicles; rates of formation of cyclic AMP and of prostaglandins. Similarly, follicles which can be prevented from ovulating by the injection of alpha-site blocking drugs, will be injected with gonadotrophins, catecholamines, cAMP, or prostaglandins in an effort to see whether the blockade can be overcome. That the blockade can be overcome with all the substances named has been already shown in chickens. The remaining problem is which of the substances are permissive of ovulation and which are obligatory. Perfusion studies are being done on rat ovaries to determine the relation of steroid synthesis to the histological health of the follicles. In both chicken and pig follicles it is now certain that steroid synthesis and steroid release into the circulation are controlled by different mechanisms. What these mechanisms are is being studied.